Mutations in preS and S gene regions of hepatitis B virus genome may cause immune escape and diagnostic escape HBV mutants. The aim of this study was to determine preS1, preS2 and S gene regions of HBV from HBV infected patient groups by sequence analysis and contribute to the relevant literature. Nucleic acid sequence analysis of preS and S genes of HBV PCR products from 56 archived plasma samples sent to Ege University Faculty of Medicine Medical Microbiology Department Molecular Virology laboratory, for HBV tests were determined by chain termination reaction. Amino acid (aa) sequences were compared with the reference sequences obtained from GenBank. Plasma samples belonged to four groups of patients: A- Chronic HBV infected patients with typical HBV serological profiles (22 samples), B-HBV infected patients with atypical HBV serological profiles (26 samples), C- HBV re-infected patients after liver transplantation (5 samples), D- Seroconversion phase following acute HBV infection (3 samples). One of two vaccine escape mutant samples was also diagnostic escape mutant; the other diagnostic escape mutant was isolated from anti-HBc positive sample. All of the sequences were determined as genotype D. HBsAg subtypes were determined as; two ayw1, six ayw3, two mix, 46 ayw2. Among the 304 codons analysed between preS 33rd and S 162nd amino acids; aa variants were determinedin 105 codons (34.5%). Sequences can be found in GenBank with accession numbers FJ001941-FJ001996. At least one aa variation was detected in 48 of 56 samples (85.7%). The amino acid variants were as follows; PreS1: A33T, A39T, P41 K, D44del, D5ON, T51P, D54N, L65P/M, F67L, W77T, A81 S, Q82E, I84T, L851/M, Q86H/T, L88S, A90T/V, N91K/del, A95P, S96A, T97I/A, N98K, Q100K, S101T, S109T, P110S, N114D/E, PreS2: M1V, Q2R, S5H, F8S, H9Q, Q13L, D14N, R16K, R18K, G19S/D, F22L/S, S28T, G30E, N33T, V39A, P41H/L, I42T/L, I45T, F46Y, S47L, R48K, I49T, D51V/G, P52L, A53V, L54R/G, N55K; S gene: E2D, I4F, F8L, G10A, V14A, F20S, L22del, R24K, P29L, Q30K, N40S, F41del, G44E, T45L, T46P, V47A, L49R, Q54R, P56L, S64F, P70A, M75I, C76Y, R79H, I81T, F83C, L88P, L94S, Y100F, Q101H/R, M103L, L104F, L109I/M, I110L, G112S/R, S113N/P, S114A/del, T115I, T116N, T118A/K, P120A/T, T123A, in "a" determinant; T126I, Q129H/R, T131N, M133T, Y134N, S136Y, S143L/M/T, D144E, G145A/R. Deletions were also found in all three preS/S gene regions. The highest number of aa variations were detectedin the isolated anti-HBc positive sample (in 24 codons), followed by liver transplant group (8-13 codons). Point mutation was detected in the preS2/S promoter CCAAT box. Major hydrophilic region (MHR) variants were determined in 41.1% of 56 samples. The highest number of MHR variants belonged to atypical HBV serological profile group (group B; 61.5%) and liver transplantation group with HBV re-infection (all C group). Among the diagnostic escape and immune escape mutant (anti-HBs positive) samples, reported MHR and "a" determinant mutations were detected. In conclusion, the study population carries HBV preS/S variants; MHR and "a" determinant variant rates are high among diagnostic or immune escape mutants. It is important to evaluate the mutant detection performance of HBsAg tests.